1. Technical Field
The embodiments herein generally relate to compression and decompression techniques, and, more particularly, to a technique for reducing buffer size for wireless analog television (TV) receivers.
2. Description of the Related Art
In recent years, techniques of transmitting or storing digital image information in a highly compressed forms or in any other forms have been popular in various apparatuses used in information distribution such as broadcasting and also in home use apparatuses (such as receivers). Image compression and image decompression examples of such forms. Image compression refers to reducing a data quantity of a digital image to such a level that it is capable of being supported by a storage medium. In a typical technique, image information is compressed using redundancy of the image information by means of an orthogonal transform such as a discrete cosine transform and quantizing.
Typically, in analog TV broadcasting, the image information is transmitted in the form of frames which are sent at a rate of 25 or 30 frames per second. Each frame is formed of a number of pixels and color information of the image frame at a particular coordinate. Red, green, and blue are the primary color components of the color image which enables receiving a desired output image. However, the received compressed information suffers wireless channel effects containing frame errors at the receiver side which is shown in FIG. 1.
FIG. 1 illustrates wireless channel effects on conventional transmitted TV frames. Each frame is formed of a number of pixels 104 (pixel is the smallest unit of a frame). The transmitted frames 102 suffer from wireless channel effects 106 which produce frame errors (letter ‘P’ turns to letter ‘F’ example for frame errors 108). Channel effects 106 are the phenomena that affect the transmitted information along its path to the receiver such as noise, distortion, and fading, etc. Thus, a backend process is required to correct these frames errors 108.
FIG. 2 illustrates a block diagram of a conventional backend process to correct the frames errors caused by various channel effects. The backend process is performed at the receiver to correct the frame errors due to various channel effects 106. The receiver corrects frame errors by comparing each pixel in the new frame 202 with the corresponding pixel in the previous frames 204. It compares the Signal to Noise Ratio (SNR) and motion per pixel to obtain a factor alpha α.
This factor indicates how much the new frame 202 depends on the previous frames 204. The previous frames 204 are stored in the memory 206. The processing unit 208 processes at the receiver comparing the new pixel with a previously stored pixel and is performed on the whole frame based on the calculation as:Displayed pixel=stored pixel(previously stored frame)*α+new pixel*(1−α).
Typically, the frame size is 320*240 pixels and each pixel is represented by 12 bits. The memory for storing one frame is 320*240*12=900 Kilobits which is a substantially large part of the receiver memory. Since the wireless receiver chip is an application-specific integrated circuit (ASIC), it has a limitations in memory size. Hence, it is not practically possible to increase the memory size. Accordingly, there remains a need to store the whole frame for the receiver without consuming the receiver's memory.